1. Field of the Invention
The present invention relates to the printing of an image in an ink-jet printer, and more particularly, to a method and apparatus for calibrating errors in image alignment on a horizontal or vertical axis.
2. Description of the Related Art
Ink-jet printers have a printhead, which is mounted on a movable carriage. When the carriage is moved in one or two directions, ink is ejected from the printhead, thus printing an image line by line. Images printed line by line collectively form the full desired image. Some inkjet printers have a plurality of printheads that operate in a similar fashion.
The quality of the full image is determined according to the number of mechanical errors. The mechanical errors cause an improper printing operation due to different horizontal or vertical printheads. In addition, the mechanical errors continuously cause printing errors according to the position of a distorted hole of the printhead.
The mechanical errors are generated due to a great variety of factors, such as curvature of a printhead, the ejection shape of different nozzles, the position of the printheads of different cartridges, and the difference in speed between printheads. In addition, speed variation and the direction of movement of a cartridge cause nonuniformity of an ink falling time.
Conventionally, a plurality of test marks are provided such that a user can check in advance the state of alignment of images to correct errors. In other words, in order to correct errors in the image alignment, a plurality of test marks are printed. The test marks are divided into test mark patterns to check an alignment state on a horizontal axis and test mark patterns to check an alignment state on a vertical axis. The user selects a test mark, an alignment state of which is the best, from the plurality of printed test marks. Then, the ink-jet printer performs a correction operation, such as selecting a printing starting position, an ink ejection speed, or ink nozzles that are most suitable for image printing. In addition, an ink-jet printer that calibrates errors of test marks automatically has been recently used.
However, the user should check the plurality of test marks to detect the alignment state of the test marks. Because this operation is performed with the naked eye, it is time consuming and the user easily gets tired. Also, there is the possibility for the user to select improper test marks. In addition, error detection is complicated even in an ink-jet printer for automatically detecting errors of test marks.